There are a number of industrial applications in which relatively large bins or containers filled with a granular or finely divided material must be emptied. In the plastic injection molding industry, for example, extruding machines require a continuous supply of small plastic pellets. These pellets are typically shipped in relatively large containers, commonly known as "gaylords", and the pellets are withdrawn from the container by inserting a vacuum hose into the receptacle, the open end of the hose being located near the bottom of the container.
In order to facilitate removal of the pellets, unloading systems have been developed in which the container is supported on a tiltable platform. The open end of the vacuum hose is positioned in a lower corner of the container and, as the container is emptied by the hose, the machine operator periodically increases the tilt of the platform to progressively lower such corner and cause the granular material to flow to that corner. Devices of this general type which are adapted to tilt containers to facilitate unloading thereof are disclosed, for example, in U.S. Pat. Nos. 2,578,116, 3,198,395 and 3,224,653.
Although unloading systems of this type have generally been adequate for their intended purposes, they have not been satisfactory in all respects. In particular, it is frequently not practical to fully tilt the platform immediately after placing the container on it, because in many applications the top of the container is open and a substantial amount of the granular material therein would flow out of the container and onto the floor. Therefore, it has typically been necessary for the machine operator to periodically and manually actuate a control to incrementally increase the tilt of the platform as the container is emptied. This is a tedious task for the operator and can lead to unnecessary delays in production if the operator forgets to tilt the platform to redistribute the material in the container and all of the material in the region of the corner having the hose is removed. Moreover, it is difficult if not impossible for a single operator to simultaneously control the unloading of more than one or two containers in an efficient manner, because the operator must carefully monitor the unloading of each of the containers and periodically actuate the control for each to further tilt the associated platform.
Accordingly, it is an object of the present invention to provide an apparatus for unloading a container which is responsive to the distribution of the material in the container and is adapted to automatically tilt the container in order to effect a redistribution of such material.
A further object of the invention is to provide an apparatus, as aforesaid, which is also responsive to the redistribution of the material caused by tilting of the container for stopping the tilting movement.
A further object of the invention is to provide an apparatus, as aforesaid, which can be safely used in an "explosive" environment.
A further object of the invention is to provide an apparatus, as aforesaid, which is rugged and dependable and requires little or no maintenance.
A further object of the invention is to provide an apparatus, as aforesaid, which is relatively inexpensive to manufacture and assemble.